fix: nested anchor tags in toc

[MohamedH1998]

Summary

Problem
When a docs page has tags: in its frontmatter, the right-hand sidebar rendered an empty ghost pill bubble before each tag. For example, a page with tags: [Postgres, TypeScript, SQL] would render six elements instead of three — one empty, one with text, per tag.
This was introduced during the TOC redesign. When the tag link markup was updated, the new (with the revised Tailwind classes and data-tag-serp-link attribute) was inserted inside the existing rather than replacing it. The outer anchor had no text content, so it rendered as an empty pill. Nested tags are also invalid HTML.

Fix
Collapsed the two nested elements back into a single anchor, preserving the updated pill styles and the data-tag-serp-link analytics attribute.

Screenshots (optional)

Before

After

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[github-actions]

This pull request requires reviews from CODEOWNERS as it changes files that match the following patterns:

Pattern	Owners
*.astro	@cloudflare/content-engineering, @kodster28

[github-actions]

Preview URL: https://c806cf5c.preview.developers.cloudflare.com
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